On Wed, Aug 21, 2024 at 8:31 AM David Hildenbrand david@redhat.com wrote:

Currently, running the charge_reserved_hugetlb.sh selftest we can sometimes observe something like:

$ ./charge_reserved_hugetlb.sh -cgroup-v2 ... write_result is 0 After write: hugetlb_usage=0 reserved_usage=10485760 killing write_to_hugetlbfs Received 2. Deleting the memory Detach failure: Invalid argument umount: /mnt/huge: target is busy.

Both cases are issues in the test.

While the unmount error seems to be racy, it will make the test fail: $ ./run_vmtests.sh -t hugetlb ... # [FAIL] not ok 10 charge_reserved_hugetlb.sh -cgroup-v2 # exit=32

The issue is that we are not waiting for the write_to_hugetlbfs process to quit. So it might still have a hugetlbfs file open, about which umount is not happy. Fix that by making "killall" wait for the process to quit.

The other error ("Detach failure: Invalid argument") does not seem to result in a test error, but is misleading. Turns out write_to_hugetlbfs.c unconditionally tries to cleanup using shmdt(), even when we only mmap()'ed a hugetlb file. Even worse, shmaddr is never even set for the SHM case. Fix that as well.

With this change it seems to work as expected.

Fixes: 29750f71a9b4 ("hugetlb_cgroup: add hugetlb_cgroup reservation tests") Reported-by: Mario Casquero mcasquer@redhat.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Shuah Khan shuah@kernel.org Cc: Muchun Song muchun.song@linux.dev Cc: Mina Almasry almasrymina@google.com Signed-off-by: David Hildenbrand david@redhat.com

Initially I thought it could be nice to split fixes for the 2 issues in separate patches in case one of them ends up needing a revert or something, but probably not worth a respin. Fixes look good to me.

Reviewed-by: Mina Almasry almasrymina@google.com

---

.../selftests/mm/charge_reserved_hugetlb.sh | 2 +- .../testing/selftests/mm/write_to_hugetlbfs.c | 21 +++++++++++-------- 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh index d680c00d2853a..67df7b47087f0 100755 --- a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh +++ b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh @@ -254,7 +254,7 @@ function cleanup_hugetlb_memory() { local cgroup="$1" if [[ "$(pgrep -f write_to_hugetlbfs)" != "" ]]; then echo killing write_to_hugetlbfs

• killall -2 write_to_hugetlbfs

• killall -2 --wait write_to_hugetlbfs

This looks correct. I don't think I expected killall not to wait.

 wait_for_hugetlb_memory_to_get_depleted $cgroup

fi set -e diff --git a/tools/testing/selftests/mm/write_to_hugetlbfs.c b/tools/testing/selftests/mm/write_to_hugetlbfs.c index 6a2caba19ee1d..1289d311efd70 100644 --- a/tools/testing/selftests/mm/write_to_hugetlbfs.c +++ b/tools/testing/selftests/mm/write_to_hugetlbfs.c @@ -28,7 +28,7 @@ enum method {

/* Global variables. */ static const char *self; -static char *shmaddr; +static int *shmaddr; static int shmid;

/* @@ -47,15 +47,17 @@ void sig_handler(int signo) { printf("Received %d.\n", signo); if (signo == SIGINT) {

•           printf("Deleting the memory\n");
  

•           if (shmdt((const void *)shmaddr) != 0) {
  

•                   perror("Detach failure");
  

•           if (shmaddr) {
  

•                   printf("Deleting the memory\n");
  

•                   if (shmdt((const void *)shmaddr) != 0) {
  

•                           perror("Detach failure");
  

•                           shmctl(shmid, IPC_RMID, NULL);
  

•                           exit(4);
  

•                   }
  

•                   shmctl(shmid, IPC_RMID, NULL);
  

•                   exit(4);
  

•                   printf("Done deleting the memory\n");
            }
  

•           shmctl(shmid, IPC_RMID, NULL);
  

•           printf("Done deleting the memory\n");
  

This seems like a simple refactor to only delete when shmaddr is set, looks fine to me.

    }
    exit(2);

} @@ -211,7 +213,8 @@ int main(int argc, char **argv) shmctl(shmid, IPC_RMID, NULL); exit(2); }

•           printf("shmaddr: %p\n", ptr);
  

•           shmaddr = ptr;
  

•           printf("shmaddr: %p\n", shmaddr);
  
  

Setting shmaddr seems correct and an oversight. I don't see shmaddr set anywhere in the current code.

            break;
    default:

-- 2.46.0

This patch has been successfully tested. All hugetlb kernel selftests pass now. # SUMMARY: PASS=12 SKIP=0 FAIL=0

Tested by: Mario Casquero mcasquer@redhat.com

On Wed, Aug 21, 2024 at 2:31 PM David Hildenbrand david@redhat.com wrote:

Currently, running the charge_reserved_hugetlb.sh selftest we can sometimes observe something like:

$ ./charge_reserved_hugetlb.sh -cgroup-v2 ... write_result is 0 After write: hugetlb_usage=0 reserved_usage=10485760 killing write_to_hugetlbfs Received 2. Deleting the memory Detach failure: Invalid argument umount: /mnt/huge: target is busy.

Both cases are issues in the test.

While the unmount error seems to be racy, it will make the test fail: $ ./run_vmtests.sh -t hugetlb ... # [FAIL] not ok 10 charge_reserved_hugetlb.sh -cgroup-v2 # exit=32

The issue is that we are not waiting for the write_to_hugetlbfs process to quit. So it might still have a hugetlbfs file open, about which umount is not happy. Fix that by making "killall" wait for the process to quit.

The other error ("Detach failure: Invalid argument") does not seem to result in a test error, but is misleading. Turns out write_to_hugetlbfs.c unconditionally tries to cleanup using shmdt(), even when we only mmap()'ed a hugetlb file. Even worse, shmaddr is never even set for the SHM case. Fix that as well.

With this change it seems to work as expected.

Fixes: 29750f71a9b4 ("hugetlb_cgroup: add hugetlb_cgroup reservation tests") Reported-by: Mario Casquero mcasquer@redhat.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Shuah Khan shuah@kernel.org Cc: Muchun Song muchun.song@linux.dev Cc: Mina Almasry almasrymina@google.com Signed-off-by: David Hildenbrand david@redhat.com

---

.../selftests/mm/charge_reserved_hugetlb.sh | 2 +- .../testing/selftests/mm/write_to_hugetlbfs.c | 21 +++++++++++-------- 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh index d680c00d2853a..67df7b47087f0 100755 --- a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh +++ b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh @@ -254,7 +254,7 @@ function cleanup_hugetlb_memory() { local cgroup="$1" if [[ "$(pgrep -f write_to_hugetlbfs)" != "" ]]; then echo killing write_to_hugetlbfs

• killall -2 write_to_hugetlbfs

• killall -2 --wait write_to_hugetlbfs wait_for_hugetlb_memory_to_get_depleted $cgroup fi set -e

diff --git a/tools/testing/selftests/mm/write_to_hugetlbfs.c b/tools/testing/selftests/mm/write_to_hugetlbfs.c index 6a2caba19ee1d..1289d311efd70 100644 --- a/tools/testing/selftests/mm/write_to_hugetlbfs.c +++ b/tools/testing/selftests/mm/write_to_hugetlbfs.c @@ -28,7 +28,7 @@ enum method {

/* Global variables. */ static const char *self; -static char *shmaddr; +static int *shmaddr; static int shmid;

/* @@ -47,15 +47,17 @@ void sig_handler(int signo) { printf("Received %d.\n", signo); if (signo == SIGINT) {

•           printf("Deleting the memory\n");
  

•           if (shmdt((const void *)shmaddr) != 0) {
  

•                   perror("Detach failure");
  

•           if (shmaddr) {
  

•                   printf("Deleting the memory\n");
  

•                   if (shmdt((const void *)shmaddr) != 0) {
  

•                           perror("Detach failure");
  

•                           shmctl(shmid, IPC_RMID, NULL);
  

•                           exit(4);
  

•                   }
  

•                   shmctl(shmid, IPC_RMID, NULL);
  

•                   exit(4);
  

•                   printf("Done deleting the memory\n");
            }
  

•           shmctl(shmid, IPC_RMID, NULL);
  

•           printf("Done deleting the memory\n");
    }
    exit(2);
  

} @@ -211,7 +213,8 @@ int main(int argc, char **argv) shmctl(shmid, IPC_RMID, NULL); exit(2); }

•           printf("shmaddr: %p\n", ptr);
  

•           shmaddr = ptr;
  

•           printf("shmaddr: %p\n", shmaddr);
  
            break;
    default:
  

-- 2.46.0